liblogger is logging framework for C/C++. It supports logging to a file/network/console transparently. It provides several logging levels and is highly customizable. Visit http://liblogger.sourceforge.net for more details.
This is the best logger in C I've found and used. I used this in embedded systems programming. It's simple, easy to customize and modify to fit to embedded systems. I'm willing to help in future development of this project.